interface CompurerAverage {
	public double average(double a,double b);
}
class A implements CompurerAverage {
	public double average(double a,double b) {
	double aver=0;
	aver=(a+b)/2;
	return aver;
	}
}
class B implements CompurerAverage {
	public double average(double a,double b) {
	double aver=0;
	aver=Math.sqrt(a*b);
	return aver;
	}
}
public class Example6_4 {
	public static void main(String args[]) {
	CompurerAverage computer;
	double a=11.23,b=22.78;
	computer = new A();  
	double result = computer.average(a,b);
	System.out.printf("%5.2f和%5.2f的算术平均值:%5.2f\n",a,b,result);
	computer = new B();  
	result= computer.average(a,b);
	System.out.printf("%5.2f和%5.2f的几何平均值:%5.2f",a,b,result);
	} 
}
